Tilt rotor Aircraft

Tilt-rotor aircraft have only recently entered the civilian market with the Agusta-Westland AW169. Yet, these aircraft, which theoretically combine the best capabilities of a helicopter and a fixed wing propeller-driven airplane, have existed for some time in the military aviation community, most notable in the form of the US Marine Corps’ VH-22 Osprey transporter. But what, exactly, sets a tilt-rotor apart from its cousin, the helicopter, or its other cousin, a turboprop?

The civilian entry into the market is in the form of the AW-169, which is a civilian version of the VH-22. This aircraft has two counter-rotating rotors mounted on engine nacelles, driven by a single turbofan engine for each nacelle. What makes this aircraft unique is that these nacelles, or pods, can rotate. And in doing so, they take the AW169 from flight characteristic of a helicopter, in terms of ability to hover and maneuver, and turn it into a fixed wing turboprop.

The nacelles of the AW169 are mounted on the aircraft’s wings. Wings on a helicopter may seem sacrosanct, but in this instance, its what allows the aircraft its impressive maneuverability. The wings contain hydraulically operated control surfaces to aid in fixed wing flight, and the nacelle gears-those that allow the massive rotors to rotate from a upward position to a forward facing position- and motors are hydraulic as well. By placing the aircrafts engines at the end of the hollow wings, which store fuel, this allows the aircraft to contain much more within itself.

Further, the configuration of the tilt-rotor allows for an impressive amount of lifting ability. In testing, the AW169 had been able to lift almost 10,000 lbs. Although this has not been certified, nonetheless it remains a spectacular feat for any helicopter, and opens the door to the possibility that the AW169 may, one day, replace the Sikorsky Skycrane as the heavy lift helicopter of choice on the civilian market.

Although the AW169 is new to the market and is, at the time of this writing, pending FAA certification, Agusta-Westland has stated that it is no more difficult to fly than a standard configuration helicopter. Further, Augusta Westland will offer AW169-specific training for the aircraft. The FAA< meanwhile, is deciding whether or not additional licensure, type-rating, or endorsements will be needed for the tiltrotor, which has not been priced as of yet.

Still, the AW169 represents an exciting new dimension to the helicopter world, and one this author hopes to experience in the near future. So if you happen to buy one, give me a call-I’d love to ride in the right seat with you!

What Does a Cyclic Stick Do?

The cyclic stick in a helicopter is, by far, the most important of all the controls in a modern helicopter, and yet, it is often the least glamorous. Located between the pilots legs in all but a few helicopter, this stick is the pilots link to telling the aircraft what he wants it to do. But how, exactly, does the funky stick work?

Well, the cyclic controls the direction of flight by changing the angle of attack of the rotor blades. The servo motors that control the angle at which the blades meet air are control-led by the cyclic. In most helicopters, there is also a twist throttle that controls the amount of power the engine produces. This throttle is what I like to refer to as ‘the potential’. As you give the aircraft ‘potential’, now you have to learn what to tell it to do with the power.

For instance, if I have my cyclic perfectly centered, and twist the throttle, with my anti-torque pedals controlled, my aircraft will simply make a lot of noise and act as a big fan. But with a little action for the cyclic, now I can gain altitude and climb while not moving laterally. If I push the cyclic forward, the nose of the aircraft will dip as it attempts to move forward. If I pull the cyclic back, the nose will raise, and the aircraft will being to climb.

You can move the cyclic side to side to cause the aircraft to bank, and of course the anti-torque pedals, which control the tail-rotor, can be used to ‘spin’ the aircraft to point in the direction you want it to go. Once the nose is in the direction you want it to be facing, you can again use the cyclic to control altitude, speed, and direction. However, in a helicopter, the aircraft doesn’t have to be pointing in the direction you want it to go- you can ‘bank’ the aircraft, or have it move sideways without any forward movement or cornering, by simply moving the cyclic sideways.

The majority of newer helicopter also have a radio and, if so equipped, autopilot controls on the cyclic’s handle. Military and law enforcement helicopters, and well as rescue helicopters, may have the controls for a camera system or thermal imager, or a spotlight, one the cyclic handle as well. In a military attack helicopter, the controls for the aircraft weapons are typically mounted on this handle, making the cyclic by far the most important control in the helicopter.

In conclusion, all pilots should be intimately familiar with their cyclic stick control in the aircraft they intend to fly. By simply taking 10 minutes to become comfortable with the different layout of the cyclic, and of course performing a pre-flight by moving the actuating the cyclic to engage the servos up in the rotor assembly, you can be assured that you’ll avea great and safe flight.

Controlled Flight into Terrain Avoidance

Controlled flight into terrain is the technical term for crashing your helicopter into the earth. This is not just into the ground-it can also man into a hill or mountain. And it happens quite often to both fixed and rotor-wing aircraft, although we’ll be focusing on the helicopter aspect of things, obviously. CFIT accidents are a major safety concern for helicopter pilots, and yet these accidents are often quite difficult to explain because they involve a pilot being aware of the impending disaster.

The most common factor in CFIT accidents is that the outside visibility is limited, or the accident occurs at night, and you can’t see the terrain features due to darkness until you’re moments away from impacting it. Another common factor with CFIT accidents is a lack of situational awareness, but vertical awareness as well. Knowing not only where your helicopter is in relation to the ground, but the terrain features around your flight areas, is the best way to prevent a CFIT accident.

The best defenses a pilot can have to avoid a CFIT accident is Training, Planning, and Preparation. Taking a few minutes before takeoff to become familiar with the proposed flight and any terrain obstacles in the flight path can go a long way towards preventing a CFIT accident. Pilots must also ensure they have adequate visibility to fly their aircraft safely. Whether this means that they can see with the naked eye, or have suitable instruments on board, or even night vision equipments, if you can’t see the terrain and obstacles around you, you’re flying into a CFTI-conducive condition.

Practicing flying with instruments while you can see with the naked eye is the best way to get comfortable with potentially needing to rely on instruments alone to guide you safely. Pilots should practice immediate CFIT avoidance procedures, such a rapid altitude increases and aerial avoidance maneuvers, in an area free of actual hazards. Pilots should also ensure that their altimeter works properly before takeoff.

Today’s modern aircraft have sophisticated electronic safety and autopilot, auto throttle, flight director, and flight management systems. No matter how face your helicopter is, however, ultimately, the pilot is responsible for CFIT avoidance. If you rely on an autopilot, crosscheck it with your instruments and your eyeball frequently failure to do so is practically begging for a CFIT accident). Caution should also be used while using illumination inside the aircraft, for certain colored lenses and lights could bleach out symbols on a map, or blind the pilot from seeing outside obstacles.

The FAA has a CFIT avoidance checklist, published by the NTSB, available on its website. I highly encourage you to download it and keep it handy. Remember, there’s no cute bear that says “only you can prevent CFIT accidents!” However, if you enjoy the controlled landing part of a helicopter flight, be responsible and know your surroundings. Fly only in conditions you’re comfortable with, and ensure your instruments work properly before flight. Safe flying is in your hands. I might not be a bear, but I’ll remind you anyways!

Purchasing Your First Helicopter

Deciding to invest in a helicopter of your own is a big step for anyone, and especially if you’re a new pilot. But if you’ve got the means to do so, it also means freedom. No longer will you be subject to flight school schedules or rental schedules in order to fly-you’ll be able to lift off any time you want! Of course, there are a few factors you’ll need to take into account first, which are covered below.

First, you’ll need to decide on the model of helicopter you want. A common beginner’s helicopter is a Robinson R-22 (2 seater) or R-44 (4 seater), both of which can be bought for less than $500,000. These are piston engine helicopters; Robinson also makes a turbine, the R-66, which starts at $895,000. Another common aircraft is the Eurocopter EC-135, a four seater, or the McDonnell Douglas MD530, both turbine powered and relatively ($1.2m) inexpensive beginner-friendly aircraft.

You’ll need to register your helicopter with the FAA, and receive a ‘N’ number. Helicopter registration fees are different than fixed wing aircraft registration fees, and they change year to year and are based on the helicopter’s characteristics. Visit www.faa.gov/registration for more information and to fill out the application. In order to register, you’ll need the serial number of the aircraft and transponder information- all of this is found on your purchase forms.

You’ll also need insurance. Would you drive a $500,000 car without insurance? Neither should you fly a half million dollar, or more, helicopter without insurance. Common brokers include Lloyds, Farmers, and AFAS, though other carriers exist. You should ensure that your policy is valid in all situations that you intend to fly in, and in all locations you intend to fly to.

You’ll need somewhere to park your helicopter when not in use. Most commercial airports have hangers available for rent, or ground tethers, which are cheaper than covered hanger space. Not all commercial airports rent space for helicopters though, so check with your airport authority for details and prices.

Finally, you’ll need a helicopter license from the FAA. A Helicopter Pilots License (Rotorcraft) is just that- a license to fly a helicopter. There are whole blogs written on getting your license, so I won’t go into details here, but more information can be found at www.faa.gov/licensure. You should keep a copy of this on your person at all times while operating your helicopter.

Congratulations, purchasing your own helicopter is a big step, and I wish you the very best of luck with your new aircraft. Just remember, don’t try and cut costs at the expense of safety. Parking your helicopter at the local grocery store park lot, instead of a hanger, might land you in jail!

Engine Types in Commercial Helicopters

In all commercial helicopters, and by and large all helicopters period, there are two main engine types. There are piston engine, and turbo shaft engines. You’ll often see either type mentioned in literature, but what’s the difference?

In a piston engine, the engine inside the helicopter is similar to one that is in your car. These use a reciprocating set of pistons to drive a drive shaft, which is turn is connected to the gearbox and the rotor head. Many training helicopters use reciprocating engines because they are fairly inexpensive to operate, and relatively simple compared to turbines. However, they produce much less power than turbine engines, and thus, are unsuitable for most heavy applications.

In a turbo shaft, or turbine, engine, the gay turbine is made up of a compressor, a combustion chamber, the turbine itself, and an accessory gearbox. The compressor draws filtered air into the combustion chamber, and compresses it. This air is directed into the main combustion chamber through discharge tubes, where atomizes jet fuel is injected into it. The fuel air mixture is ignited, and allowed to expand. This combustion gay is then forced through a series of wheels, like a windmill’s’s blades, which forces them to turn.

The spinning of these wheels provides power to both the engine’s shaft, which turns the main rotor head(s), and an accessory gearbox, which is often used to generate electrical power for the aircraft in flight. Power is provided to the two rotor systems though the accessory gearbox power output shaft, which sticks out of the turbine unit and connects to the main rotor shaft, which sticks out of the turbine unit and connects to the main rotors gear assembly. The turbine’s turbine wheels also provide power to the compressor on the engine itself, thus allowing the process to continue operating.

The exhaust gas is then, finally, expelled through an exhaust outlets. The temperature of the gas is measured at different locations throughout the process, depending on the manufacturer. But a few common terms are the inter-turbine temperature (ITT). which measures the temperature inside the spinning turbines; the Exhaust Gas Temperature (EGT), which measures temperature inside the exhaust pipe; and the Turbine Outlet Temperature (TOT), which measures temperature at exactly the point where the exhaust gas exits the turbine arrays.

Most helicopters have a single turbine; however, many are twin-turbine aircraft, especially in high-reliability situations and where more power is needed. Turbines, unlike the piston engines in training and personal aircraft, require Aviation grade kerosene, also known as JET-A fuel, to operate properly, whereas most piston engines for aviation use operate on 100LL fuel, a type of AVGAS that has a low lead content. Neither is suitable to operate on automotive petroleum or diesel, although JET-A and Diesel Fuel have many similarities. Regardless of the type of engine your helicopter uses, make sure you match it up with the proper fuel in order to avoid catastrophic failures and potential fires.

Common Emergency Equipment in Helicopters

Every pilots should be prepared for emergencies, and helicopter pilots are no exception. Emergencies often happen when we least expect it-hence the nature of the word-and as such, you should prepare for one to occur every time you get on board your aircraft!

When preparing for an emergency, every pilot should keep a minimum of emergency supplies on board at all times during flight- after all, you’re better off having it and not needing it, then needing it and not having it. That’s not to say that its wise or necessary to carry around the whole kitchen sink, but a basic assortment of supplies is something you should never leave home without.

To remember what to bring, I like to use the acronym <b>OH SHIT</b>!

O- Optics. This include some sort of signaling mirror, a flashlight, and spare batteries, as well as signaling flares.

H- Heat. You should carry matches, as well as some king of stove or means of providing heat for cooking, such as a chemical heater. Bet you should also carry a sleeping bag for each passenger and an emergency blanket when temperatures are below 40 degrees. Include a tent if flying in wilderness areas.

S- Sharp Object- This includes a flexible saw, an axe with at least a 28′ long handle, and a fixed blade knife of good quality.

H- Hope. This should come in the form of a portable electronic emergency locator transmitter, with spare batteries.

I – Idiot Proof Items – Compass, prepacked meals, and sealed water bottles.

T- Thermals. This one is simple- a pair of long underwear can go a great distance when you’re stranded in the wilderness.

As you can no doubt tell, this is by no means a comprehensive list. However, these basic supplies will handle the vast majority of emergency landing situations that a helicopter pilot will find him or herself in, and allow them to survive-along with their crew and/or passengers, long enough for a rescue teams to encounter them and bring them in safely. Also, the most important thing to do is NOT PANIC. As long as you keep your head on your shoulders, and have remembered your OH SHIT! List, you’ll be just find long enough for authorities to come rescue you! Emergencies happen to the best and worst of us; the only thing you can do about them is to prepare to survive one!

What Type of Helicopter is Right for Me?

This is a lot like asking, “What type of food with I like?” That is because, the answer is the same-there is no one right answer. Each application is generally suited to a specific type of aircraft however, given as Helicopters are incredibly versatile platforms, a helicopter may prove to be ‘good’ at handling a wide variety of tasks that it wasn’t necessarily engineered to do.

There are a few basic guidelines that you might use to select a helicopter, which include ease of flying, utility features, costs, and type. By far, the most common starter helicopter for new pilots and owner is either the Robinson R22 (2 seater) or r44 (4 seater), which is a piston-engined, single rotor helicopter that looks a little funky but is fairly easy to fly. One the other end of the spectrum, a common VIP transport aircraft for corporations is the Sikorsky S-72; fully optioned out, it can bring a price tag of nearly $20m USD, whereas the Robinsons cost less than $450,000.

Another factor to consider is what your intended use of the helicopter is. A helicopter design to, say, do sightseeing may not need the capabilities of a helicopter designed to sling logs underneath it for helilogging operations. Eurocopter, Boeing, Sikorsky, Robinson, Augusta-Westland, and Bell are common manufacturers that offer aircraft to fit a wide variety of applications and budgets. But a simple chart below, to show you-generally-what aircrafts are available in your price range.

Price Intended use Available Models
$5m + Corporate/Executive Sikorky S-75, s72, Ag/West K2/K3
$1-5m Utility/Touring/Med AW k2, EC145, Bell LongRanger
$500k-1m Sport/Sightseeing EC135, Robinson r66, Bell Jet Ranger
Under 500k Training/Personal Robinson r22, r44, and Schweitzer Helicopters
$100 Fun R/C Helicopter sold at the Kiosk at the mall

By no means is this chart comprehensive. There are hundreds of models available, from specialty (think Sikorsky Skycranes) to build-it-yourself (Rotorway Kit Models) and even NOTAR and double main rotor aircraft. A visit to your local dealer will tell you more, but the bottom line is this- only you know what helicopter is right for your intended application, so plot this out before you buy!

What makes a helicopter fly?

A helicopter has no wings. It has no propellers or jet turbines. Yet it manages to get off the ground with ease, thanks to its big rotor blades. But these are point up, you might say, so how do they propel it forward? The basic concept is this: As the blades spin, each blade acts like a mini airplane wing as it cuts through the air. Just like an airplane wing, it had a trailing edge, a leading edge, and a camber line. The camber line splits the rotor blade between its top and bottom edges (if the rotor blade was a hamburger, the camber line would be the meat). When an object, such as a helicopter, and the atmosphere move relative to on another, and the object (in this case the helicopter) cause the atmosphere to flow is a direction perpendicular to that flow, the force require to do this work causes and equal and opposite force that is lift.

In a helicopter, there are four factors that affect the amount of lift generated. These include density of the air, the speed of the airflow, the total area of each rotor blade, and the angle at which the rotor blade meets the air.

But how does this work? Well, the airflow meeting the leading edge of the rotor blade is forced to split over and under the object. The sudden change in direction of airflow over the rotor blade as it chops through the air causes an area of low pressure to form behind the leading edge, on the upper surface of the blade. In turn, due to the pressure gradient and the density of the airflow, the flow over the blade is accelerated down along the top of the blade. At the same time, however, the airflow forced under the blade is rapidly slowed, which causes an area of high pressure.

Since the two sections of airflow leave the trailing edge of the rotor blade with a downward momentum, this causes lift, as the downward momentum must have an equal and opposite reaction, or in simpler terms, upward momentum.

Additional lift is provided pursuant to Newton’s Third law or Motion, which states that for every action there is an equal and opposite reaction. You’ll note this is applied above, but it’s equally important here. When air that strikes the lower surface is directed immediately downward, it too, helps generate lift, and this allows the helicopter to remain airborne.

Although it may seem complicated, the basics of why a helicopter flies are fairly simple. Without lift, you’d simply have the world’s most expensive box fan on the ground, or the worlds most expensive hedge trimmer is you managed to roll the aircraft close to some hedges! Thankfully, you’ve got lift, and you can leave the ground safely and efficiently to continue on to your destination.

Hovering in a Helicopter

Helicopters, unlike fixed wing aircraft, can hover; that is to say, they can remain in one position without moving forward of backward, or side to side. In order to do this, the helicopter pilot has to make sure that four factors are considered: the lift, the weight, the thrust, and the drag. Many pilots believe hovering is the most challenging part of flying a helicopter, and yet the basics are simple.

The helicopter has a weight. For out purposes, lets say that this is 8,000 pounds. In order to counter the effects of gravity, the amount of lift that the rotor and aircraft generates has to be almost equal to 8,000. A pound or two isn’t going to make a noticeable difference, but several hundred pounds will. Additionally, the helicopter generates its own wind (from the rotating blades) while in a hover, and the pilot has to counter these as well to successfully hover.

The pilot must provide enough trust (forward motion) to counter any wind currents and drag that are acting on the helicopter, and they must be able to counter any tail rotor thrust that the aircraft generates itself. The power has to be enough to turn the tail and main rotors, and overcome the inherent drag that the aircraft produces.

While in a hover, the amount of thrust that the main rotor generates can be changed to maintain or alter the hovering altitude. In order to do this, you change the pitch of the blades themselves, which changes the drag on the rotors, and simultaneously the engine power must increase to keep the main rotor speed constant (more power is needed to overcome the drag created by the steeper blade angle).

The ability of a helicopter to successfully hover is generally linked to its pilots abilities; although all helicopters are capable of hovering, not all pilots are capable of executing a successful hover. This is the difference between helicopter pilots and plane pilots. Hovering is among the unique capabilities of a helicopter that sets it apart from fixed wing airplanes. All pilots should aspire to being able to execute a successful hover.

And don’t forget, the only time a fixed wing aircraft matches a helicopter ability to remain stationary on the horizontal and vertical axis , is on the ground! If a fixed wing plane attempts this in the air, I certainly wouldn’t want to be in it!

Tail Rotors and Anti-Torque Controls

For any of those who have ever seen a helicopter, you likely know that it has a tail rotor, or some form of outlet (in the case of a NOTAR-Equipped aircraft) at the rear of the tail boom, in order to counter the main rotor’s torque. But what, exactly, does this do?

Well, the tail rotor (and we’ll focus on that, since NOTAR aircraft are far and few between) acts like a ‘stop’, to prevent the body of the aircraft from turning in opposite direction of the main rotorhead. The pitch of the rotor blades is controlled by (generally) anti-torque pedals installed in the floor of the cockpit. Using these, you can adjust the pitch (angle) of the rotor blades, and thus control the direction of their thrust. By doing so, it cause the tail boom to move in the direction you desire, turning the aircraft.

So why is a tail rotor essential? Well, if you don’t have one, your helicopter body would spin wildly as an opposite reaction to the main rotor spinning in the opposite direction. Generally, helicopter that spin wildly don’t make it very far towards their destination. On the plus side, however, if you happen to bring some fruit salad along, you’ll have a nice smoothie when you’re through, as you’ll be spinning around like a turbine powered blender!

The pedals inside most helicopters are fairly straightforward to operate: push the right pedal forward, and the tail will scoot left, causing the aircraft to turn right. Pushing the left pedal forward causes the opposite effect. The controls are similar on NOTAR-equipped helicopters, except that instead of controlling the pitch of the propeller, it controls the direction of thrust nozzles built into the tail boom.

The only helicopters that do NOT have a rear-mounted anti-torque system are those with tandem rotor heads and dual rotor heads. Tandem rotor helicopter platforms have the two rotors (on the same mast) rotating in opposite directions, which counters the torque generated by the opposite rotor. However, these helicopters STILL have anti-torque petals, to control the direction of the helicopters movement in flight.

Each and every helicopter, although designs do vary, needs some means to counter the torque created by the main rotor head. This is a basic law of physics: each action has a separate and equal opposite reaction. So if you want your helicopter to fly normally, by sure to verify it has a functioning tail rotor, coaxial rotor, or thrust nozzles system to ensure you can control the torque generated by the main rotor. Alternatively, if you find yourself with a means to counter the main rotor’s thrust, you could sell tickets to what’s just become among the most expensive amusement rides ever created; a sort of ‘spinning teacups’ from hell.

(No Anti-Torque System (Tail Rotor) = Tea Cups from Hell)